When horizontally continuous-casting steel, for example, the usual practice for casting the steel comprises: connecting the lower part of the side wall of a tundish to a mold so that the extracting direction of a cast strand may be horizontal; teeming molten steel into the tundish from above; and, continuously extracting the molten steel in the tundish through the mold in the form of a cast strand while cooling the molten steel by the mold, thereby continuously casting the steel.
FIG. 1 is a sectional view of the connecting part between a tundish and a mold in a conventional horizontal type continuous casting machine for steel. In FIG. 1, 1 is the side wall of a tundish; and, 2 is the main body of a water-cooled mold. The tundish side wall 1 comprises a steel shell 3 and bricks (not shown), made of a refractory material, arranged inside the steel shell 3. The water-cooled main mold has a mold body 2 and a mold jacket (not shown) arranged outside the mold main body 2 for circulating cooling water for cooling the main mold body 2. The molten steel outlet of the tundish side wall 1 has the following structure: a seating ring 5 is attached to the part of the inner surface of the steel shell 3 which forms the periphery of a molten steel outlet hole 3a pierced through the steel shell 3, and a front nozzle 7 having a concave portion for receiving a feed nozzle 9 which engages with the inside of the seating ring 5 through joint material such as mortar. The seating ring 5 is fixed to the steel shell 3 by piercing a plurality of clamping bolts (not shown) fixed to the seating ring 5 through the steel sheel 3 and then tightening these bolts by respective nuts (not shown).
As shown in FIG. 1, a break ring 8 is fitted to the inlet opening of the main mold body 2 through a joint material such as mortar. One end of the feed nozzle 9 is in contact with the break ring 8 through a joint material such as mortar. The other end of the feed nozzle 9 is in contact with the front nozzle 7, through a joint material such as mortar. Thus, molten steel contained in the tundish is supplied through the front nozzle 7, the feed nozzle 9, and the break ring 8, into the main mold body 2. Although not shown in FIG. 1, the tundish side wall 1 or the inlet end of the main body 2 of the water-cooled mold is equipped with a connecting mechanism for connecting the tundish and the water-cooled mold. The connecting mechanism has such fastening means as a plurality of bolts and respective nuts for tightly connecting the tundish and the water-cooled mold.
The above-mentioned conventional connecting mechanism applied between the tundish and the water-cooled mold has the following problems. The tundish and the water-cooled mold are connected with each other only by a tightening force of a certain fixed value established by the nut of the conventional connecting mechanism. Therefore, such tightening force of a certain fixed value fits the break ring 8 to the inlet opening of the main mold body 2, causes one end of the feed nozzle 9 to come into contact with the break ring 8, causes the other end of the feed nozzle 9 to come into contact with front nozzle 7, and causes the front nozzle 7 to engage with the seating ring 5. Accordingly, the feed nozzle 9, for example, is affected by the heat of the molten steel which is supplied from the tundish to the water-cooled mold, but the expansion of the feed nozzle 9 caused by this heat is constrained by the above-mentioned tightening force of a certain fixed value. Each of aforementioned joint materials contracts through drying and under the influence to the heat of the molten steel. Furthermore, the front nozzle 7, the break ring 8, and the feed nozzle 9 are affected by vibration caused when extracting a cast strand from the water-cooled mold. For these reasons, the joint materials provided between the break ring 8 and the main mold body 2, between the feed nozzle 9 and the break ring 8, and between the feed nozzle 9 and the front nozzle 7 are easily susceptible to cracks and tend to have a local peeloff. This results in the problem of the molten steel leaking from cracks which form in said joint materials.